Method of preparing halogen-substituted aliphatic hydrocarbons



1963 A. JACOBOWSKYETAL- 3,079,444

METHOD OF PREPARING HALOGEN-SUBSTITUTED ALIPHATIC HYDROCARBONS Filed Dec. 1, 1958 COBOWAP ZK B MIN JA 2 AR KURT SENNEWALD BY (2mm: @4215 THEIR ATTO RN 5 United States Patent 3,979,444 METHOD OF PREPARlNG HALGGEN-SUBdTI- TUTED ALIPHATliI HYDRSEAREEQNS Armin dacobowsisy, Knapsaclr, llezirlr Kola, and Kurt Senuewald, Knapsaclr, near Kola, Germany, assignors to Knapsacir-Griesheim Alrtiengesellschalt, Knapsaclr, near Koln, Germany, a corporation of Germany Filed Dec. 1, W58, 5st. No. 77'7,5l=3 Claims priority, application ermany Dec. 27, 1957 8 Claims. (ill. ass-s54 The present invention relates to a method of preparing halogen-substituted aliphatic hydrocarbons and is a continuation-in-part of US. patent application Serial No. 359,366 filed June 3, 1953 (now abandoned). US. Patent No. 1,811,959 describes a process of preparing polymerization products of acetylene or vinyl halides by contacting acetylene with a catalyst, which consists of cuprous chloride, in the presence of ammonium chloride or a tertiary amine and hydrochloric aci As is known, cuprous chloride may also be replaced by a mixture of cupric chloride and copper.

it could not be foretold, but it was a surprising fact that by the use of cupric catalysts, but without the simultaneous use of metallic copper and ammonium chloride, the reaction of the acetylene could be conducted in such a way that other products would be produced nearly quantitatively.

The present invention relates to a process of preparing halogen-substituted aliphatic hydrocarbons from unsaturated hydrocarbons having a triple bond and cupric ialides in the corresponding hydrohalic acid solution. It is thus possible, for example to pass acetylene through a cupric-salt solution or" bydrohalic acid, so that trans 1,2 dihalide ethylene is obtained in a high purity and the cupric-salt is quantitatively reduced to cuprous-salt. This reaction, for example the conversion into trans 1,2 dichlomethylene.

2CuCl C 3 Cu Cl ClHC CHCl occurs in the liquid phase, advantageously at a temperature below about 150 0, preferably at about 60 C.about 1 08" C. Application of pressure at correspondingly higher temperatures may also be employed. The range of ressure wherein the process or" the present invention can be carried out has an upper limit at about 1.5 atmospheres gauge pressure, i.e. the highest pressure normally admissible for safety handling acetylene. The lower limit of the pressure range is at about 100 mm of mercury by gauge pressure. The dichloroethylene formed is distinguished by a high purity and boils at 48 C.

The copious-salt is reoxidized by oxygen or air in the presence of a hydrogen halide which may contain halogen as an impurity or it may be reoxidized by halogen or at an anode, for example, as follows:

Cu Cl +2HCl reoxidized at an anode=2CuCl +H and can then again be used for the preparation of ethylene dihalide.

The new process is fundamentally dillerent from the hitherto known processes and shows a number of great advantages.

For example trans 1,2 dichloroethylene is obtained, as is known, only in he gaseous phase from chlorine and acetylene, while using a capillary or a narrow tube and applying a high temperature. As catalysts, glass, sand, iron, active carbon and the salts of iron, copper and barium in the solid state may be used in that case. T he products formed contain, in addition to trans 1,2 dichloroethylene, also varying quantities of other chlorinated hydrocarbons,

39%?99 2 Patented Feb. 25, 953

such as cis 1,2 dichloroethylene, 1,1 dichloroethylene, trichloroethylene, tetrachloroethanc and others.

in the process according to the present invention, there is used, however, an aqueous solution of, for example, copper chloride as a catalyst, at a low temperature and preferably with hydrogen chloride which is introduced in the gaseous state or in the form of hydrochloric acid and which may also be rendered impure by the presence of chlorine. Copper acetylide and cuprous-chloride are prevented from precipitating by the presence of the free hydrochloric acid. Coptic-chloride acts as a chlorine carrier. The product formed is distinguished by a high purity and is obtained in a high yield due to a high activity of the catalyst.

The yield obtained in one passage of acetylene depends on the height of the contact column; in the case of preparing 1,2 trans dichloroethylene from acetylene it amounts to at least of the acetylene introduce The height of the contact column is limited, if a tower is applied, by the admissible compression of the unsaturated hydrocarbon having a triple bond. It amounts to at most 12 meters, it 1.5 atmospheres (gauge pressure) are applied as admissible pressure for acetylene and the specific gravity of the contact solution is 1.3

it was surprising that cupric-chloride is well suited as a chlorine carrier, and that this new reaction can be advantageously carried out in an industrial scale.

it is evident that there exist considerable differences between the hitherto known methods of operating and the process of the present invention.

The advantages over the known processes consist in the following: instead of expensive chlorine, aqueous hydro chloric acid or by rogen chloride which may even contain chlorine can be used for the preparation of dichloroethylene. instead of mixtures of cis and trans ethylene dihalide, asymmetrical ethylene dihalide and other byproducts, there is obtained the pure trans 1,2 ethylene dihalide. 'lhe liquid phase may now be used without the observation of special precautions, and explosions will not occur contrary to the preparation in the gaseous phase when acetylene and a halogen are used. An improved removal of heat is possible by the vi orous movement of the liquid phase, contrary to the known application or xed solid catalysts. Finally, the yield is improved.

It is often difficult to utilize the large quantities of hydrogen chloride which are produced in many processes, in particular during organic chloriuations, since said quantities are industrially utilizable as hydrochloric acid only with a restricted radius of transfer and the hydrogechloride frequently contains chlorine as an impurity additionally limiting the range of its utilization. Many attempts have already been made for preparing a reutilizable chlorine from hydrogen chloride, but these attempts have not been successful from an industrial point of view.

The reaction according to the present invention is a simple process of producing, on an industrial scale, chlorinated hydrocarbons from acetylene, while chlorine can completely or partially be dispensed with, by using hydrogen chloride in the gaseous state or dissolved in water. The use of cheap hydrogen chloride which may contain chlorine as an impurity or the use of aqueous hydrochloric acid, instead of the expensive chlorine, involves a great industrial importance:

(1) According to the aforedescribed reaction trans 1,2 dichloroethylene can be prepared from acetylene and by drochloric acid, instead of using chlorine.

(2) The clichloroethylene so obtained can serve according to known processes, as starting material for the preparation of tetrachlorethane wherein, consequently only half of the chlorine bound originates from elementary ever, only 1 mol of chlorine and 1 mol of cheap hydrogen chloride are necessary.

(4) Finally,-asymmetrical dichloroethylene (vinylidene chloride) which is of particular importance for the preparation of synthetic fibers can solely be prepared from acetylene and cheap hydrochloric acid by adding according to a known process the cheap hydrogen chloride in 1,2 position to the dichloroethylene prepared as described by (l), and splitting oil hydrogen chloride from the 2,1 position of the trichloroethane formed.

It has thus become possible to utilize hydrochloric acid or hydrogen chloride or mixtures of hydrogen chloride and chlorine, which are obtained in many processes as worthless products, in a simple manner for the preparation of trans 1,2 dichloroethylene from acetylene.-

The lower limit of the hydrochloric acid concentration to be applied in the contact solution is given by the solu* bility of the cuprous-chloride produced during the process and the upper limit is given by the boiling point of the azeotropic mixture of water and hydrogen chloride. These limits'can be ascertained for everyone skilled in the art by mere observations since in the case of a low hydrochloric acid concentration the cuprous-chloride precipitates from the solution and in the case of a higher hydrochloric acid concentration than that aforesaid gaseous hydrogen chloride escapes from the contact solution into the gas cycle.

When trans 1,2 dichloroethylene is prepared from acetylene, the most advantageously applied hydrochloric acid concentration in the contact solution amounts, for example, from about 5 to about 6 mols per liter of contact solution, corresponding to a content of about 12% to about 18% This'acid concentration range, however may extend from 2.5 to 20%.

The content of cuprous-salt may vary within wide limits. The content according to the method of operating may vary between a molar proportion of cuprous-salt and cupric-salt from about Izabout 1 to about 9zabout 1; this corresponds to a content of cuprous-salt of about 45% to about 90%.. A preferred range is about 4:1 to about 9zabout 1.

The following methods of operation are described hereafter, without, however, limiting the application thereto; they are illustrated, by way of example, in'the accompanying diagrammatic drawings:

(1) The formation of the ethylene dihalide and the oxidation of thecuprous-salt may be performed continuously in two separate reaction vessels, for example, in the towers 1 and 2 of FIG. 1. Theuns'aturated-hydrocarbon having a triple bond, for example acetylene, is caused to enter'into the apparatus at 3 and is introduced, by way of a pump 4,

a tube 5 and through a nozzle 6 into the tower 1. The tower 1 may be given the desired temperature by means of iacket 7. The tower 1 is filled, up to 8, with-cupric-halide in. aqueous, concentrated hydrogen chloride.

The reaction'prodnct, for example trans 1,2 dichloroethylene, is entered into a system of tubes 9, is conductedinto a drying tower 10, which is filled, for example, with CaCl and passed on to' a heat exchanger 11. After the condensation is complete, it flows through a tube 12 into a supply vessel 13. The portions of the reaction product which have not taken part in'the condensation in the heat exchanger 11 and which may consist, for example, of nonconverted acetylene, are passed through tube 14 and reintroduced into the reaction cycle beginning at 3.

The contact solution consumed during the-reaction in thetower. Linwhichsolution the cupric-halide is -reduced to cuprous-halide, is passed through tube 15 and intro- 4 duced. with. the aidof pump 16. into the reactiontower. 2., The desired temperature can be maintained in the tower 2 by means of the jacket 17. The cuprous-halide which is present in the introduced contactsolution is reoxidized by air, oxygen orchlorineso that cupric-halideis again produced. Air, oxygen or chlorine are introduced into the apparatus at 18v and are conveyed with the aidof a pump 19 and a nozzle 20 into the tower 2 which is filled up to 21 with the catalyst solution to be regenerated. The quantity of hydrogen chloride required for the regeneration. of

the contact solution leaves the supply vessel 23 in the form of a gas' or as an aqueous, concentrated solution, passes the tube 22 and then enters the tower '2.

At 24, the regenerated contact solution leaves the tower 2, flows through the tube 25 and enters at 26 into the tower 1. Tower 2 can be deaerated by way of the tubes 27 and 28 and the cock 29. j

By means of the apparatus described, it is possible con tinuously to react, for example acetylene, in the tower 1; in this case the contact solution used up is led away in the required manner through the tube 15. and in the regenerated form the quantity required is continuously let in through the tube 25.

It is also possible to operate discontinuously with the apparatus described herein. The" procedure is as follows: the contact solutionrin tower 1 is reacted, for ex ample, by the acetylene introduced until the bearable exhaustion has been reached. The supply of acetylene is then interrupted and the contact solution used up is regenerated as described above and then introduced into the tower 1. When the quantity required of the contact solution is again present in the tower 1, said tower can be supplied again with acetylene.

It is also possible to carry out the reaction as follows? The conversion of, for example acetylene into trans 1.2 dichloroethylene and the regeneration of the contact solution are carried out simultaneously, for example in the reaction tower 1. In that case the tubes 15 and 25 are omitted and in the reaction tower 1 a tube 30- is mounted which ends in a nozzle and serves for the introduction of the gases required for the oxidation, such as air, oxygen or chlorine; furthermore a tube for the introduction of hydrogen halide is necessary (similarly to tube 22 and supply vessel 23, described above).

Another method of operating is illustrated in FIG; 2 of the accompanying drawing.

Acetylene, for example,,is introduced at' 1 into the 7 tube 2 and passed with the aid of pump 3 and nozzle 4 The reaction'products, for example trans 1,2 dichlor'oethylene, are passed throughthe'tubes andthen introduced into a drying tower- 9 which isfilled, for example with CaCl The products are then passed through the tube It} and conveyed to the heat exchanger 11 from which the condensed trans 1,2 dichlordethylene flows through the tube 12 into the supply vessel 13. T1169 tion of acetylene which has not been reacted and which is admixed to the dichloroethylene'formed during the re action, is not condensed in the heat exchanger 11, but flows through the tube 14 again into the reaction tower 5.

When the catalyst solution has been used up, theinti'oduction of acetylene is stopped and the apparatus isblown through V with nitrogen which enters through pipe? 20. Following this, oxygen or some other gas capable of oxidation is introduced at 15, and, as described above;

reaches the reaction tower 5 over 2, 3 and'4 in a ni'anner analogous to that described above-and introduced-inter the reactiorrtower 5 where the 'contact solutionis regenerated; at the same time the hydrogen halide required for:

the regeneration of the contact solution is caused to leave the supply vessel 16 in the gaseous or aqueous, concentrated form and introduced into the reaction tower 5.

After the catalyst solution has been regenerated and the apparatus has been blown through via 20 with nitrogen, the above described reaction is started again while introducing, for example, acetylene.

The apparatus situated on the right-hand side of the plane given at 17 is once more present specularly on the left-hand side of the plane given at 13; the process can, therefore also be effected as follows: in the devices mounted on the right-hand side of 17 and on the left-hand side of 1., the aforedescribed reaction and the regeneration of the contact solution can take place alternately.

The apparatus can be exhausted at 19.

if pressure is applied the procedure is as follows: A mixture, 2. suspension or an emulsion of aqueous cupricsalt solution containing hydrogen halide and the ethylene dihalide already obtained is first introduced into the a paratus and acetylene and hydrogen halide are then conducted into said mixture.

Finally an intimate contact between the liquid catalyst and acetylene or oxygen and hydrogen chloride may be attained by using trickling towers, injectors, turbomixer vessels provided with stirrers and similar devices.

In general, there will be operated by the following continuous process: In the first apparatus (see tower 1 of FlG. 1) acetylene is acted for example on cupric-chloride in a hydrochloric acid solution at a temperature between 60 C. and 150 C., if required with application of atmospheric (gauge) pressure. During the reaction the trans 1,2 dichloroethylene is separated from the nonconverted acetylene by cooling, whereas in the second apparatus (tower 2) the cuprous-cllloride solution formed is oxidized again with air, oxygen or at an anode, while adding hydrochloric acid, so that cupric-chloride is obtained. The contact solution is pumped in a cycle through both devices in such a manner that the oxidized solution is continuously introduced into the first apparatus and the reduced solution is continuously introduced into the secoud apparatus. In order to improve the fixation and activation of the acetylene, a certain cuprous-conent is maintained in the first apparatus wherein the oxidized solution is taken up. The non-converted acetylene is mixed in a cycle with a fresh quantity of acetylene and reintroduced into the first apparatus.

It is possible to apply the process of the present invention also to other unsaturated triple bond hydrocarbons, for example, to monovinyl-acetylene.

The following examples serve to illustrate the invention, but they are not intended to limit it thereto:

Example 1 In a reaction tower containing a contact solution of the following composition: 0.63 mol CuCl per liter, 1.39 mol CuCl per liter (i.e., a ratio of cuprous/cupric=0.45 1) and 5.0 mol HCl per liter, there were circulated 50 l. of acetylene at 91 C. and 764 mm. Hg gauge pressure per hour. The molar ratio of cuprous/cupric set in the beginning at 0.45 :1 was maintained by adding through pumping into the contact solution a cupric chloride solution and by correspondingly drawing oi? the dissipated contact solution. Altogether 53 l. acetylene were converted and thereby 170 g. pure trans 1,2 dichloroethylene were obtained. The yield relative to acetylene was 75%; the contact-efiiciency was 21 g. dichloroethylene per liter contact solution and per hour.

Example 2 Into a reaction tower 2 liters of a contact solution were introduced containing 1.15 mol cuprous-chloride, 3.31 mol cupric-chloride and 1.01 mol HCl per liter contact solution. At a contact temperature of +65 C.

and an overpressure of 200 mm. Hg-column about 40' Example 3 In a reaction tower containing a contact solution of the following composition: 0.95 mol CuCl per liter, 1.05 mol CuCl per liter (i.e. a ratio of cu-prous/cupric=0.9:1.0)

and 5.7 mol I-lCl per liter, there were circulated 50 l. of acetylene at C. and 760 mm. Hg gauge pressure per hour. The cuprous/cupric molar ratio set in the beginning at 0.9:1.0 was maintained as described in Example 1. Altogether 94 1. acetylene were converted and 327 g. pure trans 1,2-dichloroethylene were obtained. The yield relative to acetylene was 81%; the contact-efliciency was 33 g. dichloroethylene per liter contact solution and per hour.

Example 4 in a reaction tower of 2 1. volume there was present a contact solution of the following composition: 1.09 mol CuCl per liter, 0.80 mol CuCl per liter (i.e. a ratio of cuprous/cupric=1.36: 1)

and 5.6 mol HCl per liter. In this solution 50 l. of acetylene were circulated at 90 C. and at 765 mm. Hg gauge pressure per hour. The molar ratio of cuprous/ cupric set in the beginning at 1.36:1 was maintained as described in Example 1. Altogether 50 l. acetylene were converted and 185 g. pure trans 1,2 dichloroethylene were obtained. The yield relative to acetylene was 86%; the contact eificiency was 26 g. dichloroethylene per liter contact solution and per hour. The reduced contact efficiency is explained here by the reduced total copper concentration in the solution.

Example 5 Two liters of a contact solution of the following composition were filled into a reaction tower: cuprous-chloride: 1.9 mol per liter, cupric-chloride: 1.06 mol per liter and HCl: 5.5 mol per liter. The cuprous-chloride: cupric-chloride molar ratio is 1.8:1. Into this solution about 60 liter acetylene per liter contact solution were introduced per hour at +80 C. and an over pressure of 300 mm. Hg-column, whereby the cuprouszcupric molar ratio set at the beginning was maintained by continuously adding regenerated contact solution and correspondingly drawing oil the used-up contact solution. liters of acetylene were consumed over a three hour period where 576 g. of 1,2 dichloroethylene were produced. Relative to the acetylene used, the yield was 92%. The contact performance was 96 g. 1,2 dichloroethylene per liter contact solution and per hour.

Example 6 In a reaction tower there was present a contact solution 7 and thereby 381 g pure trans 1,2 dichloroethylenewere:

obtained. The yield-relativeto acetylene was 95%; the

contact efiiciency was 43 g. dichloroethylene per liter contact solution and per-hour.

Example 7 100. hot acetylene were introduced at, about 85 C. under a pressure. of about 250 mm. of mercury into. a reaction tower: which. contains, 1.70.5. grams=1 mol of CuCl' .2H O.- and 396. grams-=4; mols; of CuCl. in. 2000 grams'ofahydrochloric acid of 20%. strength. A cupricchloride solutionpnmpedintothe; apparatus and the contact solution consumed is drawnoft; a molar ratio of about 4:about 1 of cuprous/cupric was thus adjusted. 420 grams of pure trans 1,2dichloroethylene boiling at 48 C. were obtained. The yield calculated. upon the acetylene converted amounts to 97% andthe capacity of the catalyst was about. 102-grams of dichloroethylene per liter of catalyst an hour.

Example 8 1001. of acetylene were introduced at about 90 C.

under a pressure of about 300 mm. of mercury into a.

reaction tower'which was charged with a contact solution containing 1.90 mols'of CuCl, 0.24 mol of CuCl and.

about 5.6-mols of'HCl per liter of catalyst. By a continuous addition by pumping-of a cupric-chloride solution in:

hydrochloric acid and drawing off of the reduced contact solution, a molar ratio of about 8:about l of cuprous/ cupric were maintained. 430 grams of a reaction prodnot were obtained. which boiledat 48 C. and 99.6% of which consistedoi trans 1,2 dichloroethylene. The yield.

houndoes: notdepend only upon the molar ratio, cuprous chloridelcupric chloride, but also upon the total concentration of the copper. At a given molar ratio cup rous chloride/cupric chloride. and a given HCl concentration, the maximum total concentration of copper is nearly entirely fixedby. thesolubility. of the cuprous-chloride. At the sametotal content of. copper, thecontact solutions with a lowermolar ratio. cuprous chloride/cupricchloride contain: of course less cuprous-chloride. than. at a correspondingly higher molar. ratio. So: in those, cases, with constantly lower. molar ratio,. the total concentration. of

copper canbe increasedwithoutany; difiiculty; as explained in: the description. and: examples, corresponding. to, the solubility of. cuprous-chloride. In this; manner, lower contact performances obtained at contact: solutions, with aconstanttotal concentration of. copper, while the cuprous:

chloride/cupric:chlorid'e molar ratio, is. decreasing, can be compensated, that: is, they can be. increased, again. Finally. the. methods: with the cuprous chloride/cupric chloride-molar ratio of 1.: 1 to.4:1 and. the methods with a molar ratio of only 4:1 to 9:1. then-can be considered equaL.

To state the above proposition in another way, the amount of 1,2- dichloroethylene produced is dependent on the molar ratio of cuprouschloride/cupric chloride on the one hand and the total amount of copper. present in the contact solution, on the other hand; and that the higher the cup rous chloride/cupric chloride the better the process on the onehand' and the higher the totalamount of copper the better the process on the other hand. Consequently, a-relatively'small cuprous chloride/ cupriechlorideratio, say, 1:1 togethenwith a high total amount of'coppermay give the same results as likewisedoes: a relatively great cuprous chloride/cupric chloride. ratio, say, 9:1 together with. a low total amount. of

copper.

Obviously many modifications and variations of the present invention are possible in the-light of the above teachings. It is, therefore, to. be understood that withinthe scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A process for producing trans-1,2-dich1oroalkene which comprises introducing 'an unsaturated aliphatic hydrocarbon having at least one triple bond into a solution consisting of cuprous chloride, cupric chloride, and about 2.5 to about 20% of hydrogen chloride, the molar ratio of cuprous chloride to cupric chloride being atleast 1:1, said solution having a mol total copper content of 1.3 to 5 mol per liter of. contact solution, said solution being maintained at a temperature of about 60. to 150 C., and recovering resulting trans-1,2-dichloroalkene.

2. The process of claim 1 wherein the molar ratio of cuprous chloride to cupric chloride in the reactionmixture isrfrom about 4:1 to about 9:1.

3. The process of claiml wherein the reaction is carried out under a pressure of between about 100 mm. of mercury gauge pressure and about 1.5 atmospheres gauge pressure.

4. The process of claim 1 wherein aqueous hydrogen.

chloride is used.

5. The process of claim 1 wherein the reaction is carried out in two reaction zones and includes the, steps of introducing .the unsaturated aliphatic. hydrocarbon into. liquid solution in one of said zones to form the trans- 1,2-dichloroalkene as well as to convert the cupric chloride in the solution to cuprous chloride, pumping the reduced liquid solution into the second of said zones, re-' oxidizing the cuprous chloride in said solution while it.

is in the second of said zones, and returning the .reoxidized solution to the firstv of said zones, the entire process taking place in a continuous manner.

6. The process of claim 1 wherein said unsaturated aliphatic hydrocarbon is acetylene.

7. A process for producing trans-1,2 dichloroalkene.

which comprises introducing an unsaturated aliphatic. hydrocarbon having at least one triple bond into a liquid solution consisting of cuprous chloride, cupric chloride, and about 2.5 to about 20% of hydrogen chloride, the. molar ratio of cuprous chloride to cupric. chloride being at least 1:1, said solution having a mol totalflcopper.

content of 1.3 to 5 mol per liter of contact solution, said solution being maintained at a temperature of. about to 100 C.,. and recovering resulting trans-.1,2-dichloroalkene.

8. A process for producing pure trans-1,2-dichloroethylene. which comprises introducing. acetylene into: a solution consisting of cuprous chloride, cupric, chloride and about 12 to 18% aqueous HCl, the'molar ratio, of cuprous chloride to cupric chloride being about 4:1 to

about 9: 1, said'solution having a mol total copper content of 1.3 to 5 mol per liter of contact solution, said solution. being maintained at a temperature.of'about-60to C., carrying out the reaction under apressure of between 100 mm. of Hg gauge pressureand about 1.5 atmospheres gauge pressure, and recovering resulting trans.-1,2-di chloroethylene.

References Cited in the file'of this patent UNITED STATES PATENTS Alder May'4', 1948' Thomas et al Oct. 8, 1957" FOREIGN PATENTS 

1. A PROCESS FOR PRODUCING TRASN-1,2-DICHLOROALKENE WHICH COMPRISES INTRODUCING AN UNSATURATED ALIPHATIC HYDROCARBON HAVING AT LEAST ONE TRIPLE BOND INTO A SOLUTION CONSISTING OF CUPROUS CHLORIDE, CUPRIC CHLORIDE, AND ABOUT 2.5 TO ABOUT 20% OF HYDROGEN CHLORIDE, THE MOLAR RATIO OF CUPROUS CHLORIDE TO CUPRIC CHLORIDE BEING AT LEAST 1:1, SAID SOLUTION HAVING A MOL TOTAL COPPER CONTENT OF 1.3 TO 5 MOL PER LITER OF CONTACT SOLUTION, SAID SOLUTION BEING MAINTAINED A TEMPERATURE OF ABOUT 60 TO 150* C., AND RECOVERING RESULTING TRANS-1,2-DICHLOROALKENE. 